Either direct dyes or oxidation dyes are generally used for dyeing keratinous fibers. In the case of oxidation dyes, although it is possible to achieve intense coloring with good fastness properties, the oxidizing agents used to develop these colors, such as H2O2, can result in damage to the fibers in some cases. Furthermore, some oxidation dye precursors or specific mixtures of oxidation dye precursors can occasionally induce sensitization in people with sensitive skin. Direct dyes are applied with care. However, their disadvantage is that the colorings often have insufficient fastness, especially when the hair is washed, but also due to other influences such as sunlight or reactive environmental chemicals, such as swimming pool water.
In addition to insufficient fastness, the poor coverage of gray by direct dyes is another general disadvantage. Full coverage or concealment of gray hair is considered as perfect gray coverage. If a dyeing agent with optimal gray coverage is applied to a person whose hair is, for example, 50% gray (50% of the hair is gray and 50% of the hairs are still pigmented), after applying the dye, there is a uniform color result, i.e. no perceptible difference in color between the gray and non-gray hair after the dyeing.
While good to very good gray coverage can generally be achieved with oxidative dyes, the gray coverage with direct dyes is thus far not very satisfactory. Therefore, there are few alternatives available for laminating or covering their (wholly or partly) gray hair for users who wish to avoid using oxidative hair dye due to the associated hair damage.
In addition to beautiful hair color, users want shiny hair. Shiny hair looks attractive and healthy, and the hairstyle is perceived as well cared for and vital. In many cases, the consumer has multiple wishes they would like to fulfill simultaneously: they want an attractive hair color and shiny hair at the same time. For practical reasons, they would like their hair to undergo a single treatment only.
The state-of-the-art technology already offers various methods for dying the hair in the widest possible variety of shades. But as before, there is a demand for new coloring agents, which have a high color uptake of the dyes during the dyeing process, and at the same time enable good gray coverage and produce an exceptionally high gloss.